..to make us feel better off? or is that too simplistic?
Dunno, depends if you feel others have any influence over your feelings.
Personally, I can't do the £69 trouser thing because I genuinely don't believe I will get £69 of value.
But £7.99? Yes, the endorphins would be pumping. I would get more than £7.99 value out of the trousers.
And that would be a feeling specific to me, not influenced by others.